In 60% of patients with post-phlebitic syndrome lymphography of the lower extremity shows involvement of the deep system. In 77% of the patients there was increase in the number and caliber of the deep lymphatic vessels. They frequently appear elongated, tortuous, and ectatic but usually do not show signs of insufficiency. It appears as if these vessels act as collaterals and compensate for difficiencies of the deep venous circulation. Multiple lympholymphatic and lymphovenous communications have been observed.